Alloys for low temperature assembly were developed in order to face the serious assembling conditions. In this study, the composition of the alloys was controlled so that the melting points could be in the range from 56 oC to 105 oC. The high-Sn content solders would be replaced by high-In and Bi with the addition of Sn or Ga. The alloys were reflowed on Cu substrates. Thermal properties were measured for different compositions. In-Cu or Sn-Cu compounds were formed at the interfaces and the kinetics of the formation were studied. Ball shear test was applied to the samples and the results of the joint strength were used to compare with that of the eutectic Sn-In solders. The evolution of microstructure at different reflow conditions were characterized by scanning electron microscopy (SEM), and the compositions were determined by electron probe micro-analyzer (EPMA).